海洋核杂岩   总被引：1，自引：0，他引：1  

李三忠  吕海青  侯方辉  郭晓玉  金宠  刘保华 《海洋地质与第四纪地质》2006,26(1):47-52

为了解释洋壳中大量铲形正断层及垂直洋中脊的大量线理(如大西洋中脊的巨型窗棱构造)等现象,通过与大陆上变质核杂岩对比,近来提出了一种新的海底构造类型———海洋核杂岩。在洋底深地震剖面上核杂岩结构形态可以分为3部分,其中第1部分为层1和层2,以脆性变形为特征;第2部分为脆-韧性过渡层,拆离带发育其中,由白色结壳式碳酸盐岩和强烈蛇纹石化的橄榄岩或玄武岩、超镁铁质糜棱岩、糜棱状辉长岩等组成。拆离面之上为未变质的薄层海洋沉积层,其下为热洋幔的退变质岩石组成;第3部分为核部,以塑性变形为特征,常被超基性岩体(尤其是辉长岩侵入体)底辟侵入。与大陆变质核杂岩相比,海洋核杂岩具有明显的独特性。海洋核杂岩的拆离断层同样有数十千米的位移量,因而,可能导致出现海底磁条带的局部错位现象,使得洋壳磁条带的平面结构复杂化。  相似文献   

板块俯冲带岩浆作用过程的研究   总被引：1，自引：0，他引：1  

李怀明  翟世奎  陶春辉  于增慧  季敏 《海洋科学进展》2009,27(1)

综合分析了板块俯冲带岩浆活动的物质来源、岩浆上涌直至喷出的地球化学过程以及与这些过程相对应的时间尺度等研究的进展,指出了目前研究中存在的主要问题,并建议我国在该领域开展相关的研究中应:1)首先利用独有的地理优势,以处于弧后扩张作用早期的冲绳海槽为研究对象,开展相关的调查与研究;2)积极引进先进的技术手段;3)通过加强国际合作,积极参与国际合作项目,拓展研究领域.  相似文献   

蛇绿岩岩石组合及洋脊下岩浆作用   总被引：21，自引：0，他引：21  

张旗  钱青  王焰 《岩石矿物学杂志》2000,19(1):1-7

蛇绿岩的岩石组合从下至上分为４个单元,即：变质橄榄岩单元、深成杂岩单元、席状岩墙群杂岩单元和喷出岩单元。各单元的岩石组合是多种多样的：变质橄榄岩单元主要由方辉橄榄岩、二辉橄榄岩和少量纯橄岩及斜长二辉橄榄岩组成;深成杂岩单元单元包括辉长岩－镁铁质堆晶岩和超镁铁质堆晶岩,在深成杂岩和席状岩墙群杂岩单元内在复杂的岩浆侵入事件;喷出岩单元不仅仅由玄武岩组成,还包括安山岩、玻安岩、钠长岩以及乐砾岩、凝灰岩等  相似文献   

Petrology of basic and intermediate orogenic granitoids from the Sila Massif (Calabria,southern Italy)     

A. Caggianelli  A. Del Moro  G. Piccarreta 《Geological Journal》1994,29(1):11-28

Hercynian gabbroic, dioritic and tonalitic rocks crop out in the neighbourhood of Rovale (Sila Grande, Calabria). They make up a crude rectangular outcrop with the western part consisting of gabbroic rocks and the eastern of dioritic and tonalitic rocks. They come into contact with medium to high grade metapelites on the western side and with heterogeneous granodiorites on the other sides. In the gabbroic body both opx ± ol bearing cumulates and amphibole differentiates occur and are characterized by the widespread presence of brown pargasite. Sporadic magmatic to subsolidus corona textures between olivine and plagioclase or orthopyroxene and plagioclase can be observed and their preservation clearly suggests a post-tectonic emplacement for the gabbroic magma. Diorites and tonalites display hypidiomorphic textures free of olivine and orthopyroxene and bearing green Mg-hornblende. The granitoids, on the basis of chemical data, display orogenic features of the continent-continent collision type. The gabbroic rocks have high Al tholeiitic composition and fractionation of orthopyroxene and plagioclase played an important part in their evolution. The Rb/Sr isochron method did not give a precise emplacement age for the granitoids as a whole. Initial ⁸⁷Sr/⁸⁶Sr ratios (at 290 Ma) are higher in the gabbroic body (0.7091–0.7095) than in diorites and tonalites (0.7083–0.7092). Thus gabbroic rocks appear more displaced than diorites and tonalites towards crustal isotopic composition. The eNd data seem to confirm this feature, thus suggesting that the gabbroic rocks and diorites derived from distinct mantle magma batches. Interestingly, small isotropic gabbroic masses occur within the diorites and show general features that allow them to be considered as possibly parental with respect to the host diorites. The evolution to the dioritic composition might have occurred through fractionation and minor mixing with a more acidic component such as the northern granodiorites. Geochemical, Sr and Nd isotopic data indicate a scenario of a composite plutonic body formed by distinct magma batches of mixed crust and mantle origin.  相似文献   

Anatomy of the transpressional Dom Feliciano Belt and its pre-collisional isotopic (Sr–Nd) signatures: A contribution towards an integrated model for the Brasiliano/Pan-African orogenic cycle     

《Gondwana Research》2024

The Dom Feliciano Belt evolution is reviewed based on cross-sections, space–time diagrams, P-T paths, and Sr–Nd isotopic data of pre-collisional metaigneous rocks. The belt is divided into northern, central and southern sectors, subdivided into tectonic domains, developed at Neoproterozoic pre-, syn- and post-collisional stages. The northern sector foreland pre-collisional setting represents a rift, with tholeiitic (meta)volcanic rocks (∼800 Ma) chronocorrelated to hinterland intermediate and acidic orthogneisses of high-K calc-alkaline arc signature. In contrast, the central sector records a complete section from the forearc towards the back-arc region during pre-collisional times. In the western domain, ophiolites (∼920 Ma) are associated with arc-related orthogneisses and metavolcanic rocks (880–830 Ma; 760–730 Ma). At back-arc position, continental arc-related magmatism (800–780 Ma) is registered by hinterland orthogneisses and central foreland metavolcanic rocks. Ophiolites on the hinterland opposite side comprise two compositional groups, with N-MORB and supra subduction signature, interpreted as a back-arc basin record (∼750 Ma). The pre-Neoproterozoic basement of the whole belt is correlated with the Nico Perez Terrane and Luis Alves Block (Archean to Mesoproterozoic, with Congo Craton affinity). This contrasts with the Piedra Alta Terrane (Rio de La Plata Craton, only Paleoproterozoic), westernmost Uruguay. The suture between the Piedra Alta and Nico Perez terranes is correlated with the suture zone in the westernmost central sector. Transpression affected both foreland and hinterland during collision (660–640 Ma), with high-T/low-P hinterland progressive exhumation, whilst foreland low- to medium-grade correlated sequences record underthrusting. Post-collisional processes included magmatism throughout the belt (640–580 Ma), strain partitioning along strike-slip shear zones, and foreland basin fill. Late tectono-metamorphic and magmatic processes (560–540 Ma) were attributed to the Kalahari Craton collision. Arc magmatism migration due to subduction angle variations suggests modern-style plate tectonics during Gondwana amalgamation. Diachronism and kinematic inversion are characteristic of an oblique convergent multi-plate orogenic system.  相似文献   

义敦岛弧带弧后区板内岩浆作用的时代及意义   总被引：14，自引：0，他引：14  

曲晓明侯增谦  唐绍华 《岩石矿物学杂志》2003,22(2):131-137

通过对义敦岛弧夏囊沟一带酸性火山岩的岩石地球化学和Rb-Sr同位素研究,首次在该岛弧弧后区确立了一条板内火山岩带.这些火山岩属钾玄岩系列,以高K2O,低CaO,富Nb、Ta、Zr、Hf,贫Sr、Eu为特点,具标准的"V"型稀土元素配分型式,构造环境判别图解显示其形成于板内裂陷环境.由4个全岩样品给出的Rb-Sr等时线年龄t=189.2±5.0 Ma,相关系数R=0.999?824,ISr=0.714?578.认为火山岩的成分分异受斜长石在岩浆源区熔融残留和岩浆形成后黑云母的结晶分离双重控制.位于该带东侧弧后扩张盆地中的晚三叠世勉戈组双峰火山岩的形成年龄为213.1 Ma,说明该岛弧仅仅在24 Ma左右时限内就完成了从俯冲造弧到板内裂陷的重大转换,由此可对该岛弧带的碰撞造山过程和演化时序做出精确约束.  相似文献   

铀成矿机理的统一性探讨     

伍皓  熊树银  夏彧  周恳恳  梁薇  李炼鹏  雷星 《沉积与特提斯地质》2023,43(1):59-76

为探讨不同类型铀矿床是否可能本质上都是地幔柱作用的产物，在“全球热液铀矿成因理论”和“热点铀成矿理论”等前人研究基础之上，结合岩浆岩锆石铀、钍含量研究初步揭示了：（1）铀、钍主要富集于外地核；（2）洋岛玄武岩、板内玄武岩、高分异花岗岩及伟晶岩型铀矿可能为地幔柱产物。对比国内多种类型铀矿床科研成果，总结发现有一定数量的铀矿床与洋岛玄武岩、板内玄武岩、A型花岗岩以及高分异花岗岩紧密伴生，成矿与成岩时空基本耦合。如四川攀枝花大田混合岩型铀矿和松辽盆地钱家店–白兴吐砂岩型铀矿伴生两类玄武岩；甘肃芨岭钠交代型铀矿和陕西商丹伟晶岩型铀矿区伴生两类花岗岩；粤北诸广–贵东花岗岩型铀矿区、赣南多类型铀矿区和江西相山、新疆白杨河火山岩型铀矿区伴生以上四类岩石类型。分析认为上述岩石类型可能是由地幔柱生成并起着导矿或导矿兼储矿的关键作用，据此提出铀矿“核源–地幔柱”成因认识，即：外地核是铀元素的主要发源地，地幔柱是铀运移的统一通道，铀成矿过程可能是外地核中的金属铀呈铀氢化物或铀合金氢化物等形式沿地幔柱上升迁移，直至在浅部地质体氧化聚集成固态铀矿物的过程。  相似文献   

大陆弧岩浆幕式作用与地壳加厚:以藏南冈底斯弧为例   总被引：1，自引：0，他引：1  

马绪宣  许志琴  刘飞  赵中宝  李海兵 《地质学报》2021,95(1):107-123

大陆弧岩浆带位于汇聚板块的前缘,记录了洋陆俯冲过程和大陆地壳生长过程,是研究壳幔相互作用的天然实验室.越来越多的研究发现,大陆弧岩浆的生长与侵位并不是均一的、连续的过程,而是呈现阶段性、峰期性特征,即幕式岩浆作用.弧岩浆峰期与岩浆平静期相比,岩浆增生速率显著增强,易于发生岩浆聚集,继而形成大的岩基,如北美西部科迪勒拉造...  相似文献